KR20160060693A - Intermediate temperature sodium-metal halide battery - Google Patents

Abstract

The intermediate temperature molten sodium-metal halide rechargeable battery has a relatively low melting point that allows the battery to operate at significantly lower temperatures as compared to conventional zebra battery systems and to utilize highly conductive NaSICON solid electrolyte membranes Utilize a molten eutectic mixture of sodium haloaluminate salts. The anode comprises a mixture of NaX and MX, wherein X is a halogen selected from Cl, Br and I and M is a metal selected from Ni, Fe and Zn. The anode 0 <δ <4, X '"4 , and X is Cl, Br, and selected other halogens of the formula NaAlX in I' _{- δ} X" mixed molten salt containing two or more salts, which may be represented as _δ anode Are disposed in the electrolyte. The anode may contain additional NaX added in a molar ratio of NaX: NaAlX ' _{4 - delta} X " _delta ranging from 1: 1 to 3: 1.

Description

INTERMEDIATE TEMPERATURE SODIUM-METAL HALIDE BATTERY [0002]

Related application

This application claims priority from U.S. Provisional Patent Applications 61 / 882,516 filed on September 25, 2013 entitled " Mesophilic Sodium Nickel Halide Battery " U.S. Provisional Patent Application 61 / 891,744, filed October 16, 2013, entitled " mesophilic sodium-nickel halide battery " And U.S. Provisional Patent Application Serial No. 61 / 898,617 filed on November 1, 2013 entitled " mesophilic sodium-metal halide battery ". This application is incorporated herein by reference.

Field of the Invention

The disclosed invention is directed to a mild, molten sodium-metal halide battery. More particularly, the present invention relates to a sodium / metal chloride zebra battery system that is comparable to a conventional sodium / metal chloride zebra battery system, but which has a relatively low melting point that allows the battery to operate at significantly lower temperatures Metal halide batteries utilizing molten eutectic mixtures of halosilicate salts.

BACKGROUND OF THE INVENTION A battery is a known device used to store and discharge electrical energy for many uses. To produce electrical energy, a battery typically converts chemical energy directly into electrical energy. Generally, a battery includes one or more galvanic cells, wherein each cell is made of two electrically disconnected half-cells except through an external circuit. During discharging, electrochemical reduction occurs at the anode of the cell, and at the same time, electrochemical oxidation occurs at the cathode of the cell. Although the positive and negative electrodes do not physically touch one another in the cell, they are chemically linked to one or more ionic conducting and electrically insulating electrolyte (s), which can be either a solid or liquid state, or a combination thereof. When an external circuit or load is connected to a terminal connected to the cathode and connected to a terminal connected to the anode, the battery moves the electrons through the external circuit while the ions move through the electrolyte.

The battery can be classified in various ways. For example, a battery that is only fully discharged once is often referred to as a primary battery or a primary battery. On the other hand, a battery that can be discharged and recharged more than once is commonly referred to as a secondary battery or a secondary battery. The ability of a battery or battery to charge and discharge multiple times depends on the Faraday efficiency of each charge and discharge cycle.

Sodium-based rechargeable batteries can include a variety of materials and designs. Most, if not all, sodium primary batteries that require high Faraday efficiency, solid primary electrolyte separators such as solid ceramic primary electrolyte membranes are used. A major advantage of using a solid ceramic primary electrolyte membrane is that the Faraday efficiency of the resulting cell approaches 100%. Indeed, in virtually all other battery designs, the electrode solution in the cell becomes able to mix over time, thereby causing loss of Faraday efficiency and loss of battery capacity.

Primary electrolytic separators used in sodium batteries that require high Faraday efficiency usually consist of ionic conductive polymers, ionic conductive liquids or gel-permeable porous materials, or high-density ceramics. In this regard, most rechargeable sodium batteries, which are currently commercially available, although not all, consist of a molten sodium metal cathode, a sodium beta "-alumina ceramic electrolyte separator, and a molten anode. One is the molten NiCl ₂ , NaCl and NaAlCl ₄ , commonly referred to as zebra wares. Zebra cells typically operate in the temperature range of 270 ° C. to 350 ° C. Another known molten anode is the melting, often referred to as sodium / sulfur, There is a complex of sulfur and carbon.

Because these conventional high temperature sodium-based rechargeable batteries have a relatively high specific energy density and only a moderate power density, such rechargeable batteries typically suffer from high power densities, such as fixed reservoirs and amorphous power supplies Typically used for certain specific applications requiring high non-energy densities.

Despite useful features associated with some conventional sodium-based rechargeable batteries, such batteries can have significant drawbacks. In one example, because the sodium &bgr; "-alumina ceramic electrolyte separator is typically more conductive at temperatures above about 270 DEG C and is better wetted by molten sodium and / or the molten anode typically retains the molten state Many of the conventional sodium-based rechargeable batteries operate at temperatures higher than about 270 DEG C and require significant heat management and thermal sealing issues (e.g., temperatures above about &lt; RTI ID = 0.0 &gt; Some rechargeable batteries may have difficulty in dissipating heat from the battery or maintaining the cathode and anode at relatively high operating temperatures. In another example, some sodium-based rechargeable batteries The relatively high operating temperature of the battery can cause significant safety issues. In another example, The relatively high operating temperature of some sodium-based batteries requires that its components be resistant to such high temperatures and be operable. Thus, these components can be relatively expensive. Since a relatively large amount of energy may be required to heat a sodium-based battery to a relatively high operating temperature, such a battery can be expensive to operate and energy inefficient.

Thus, although molten sodium-based rechargeable batteries can be used, there were also challenges for these batteries, including those mentioned above. Thus, replacing certain conventional hot-melt sodium-based rechargeable batteries with other molten sodium-based rechargeable batteries that can reinforce or even operate at temperatures below about 220 ° C, and more preferably below about 180 ° C It will be an advancement in related technology field.

Summary of the Invention

The presently disclosed invention is directed to a mild, molten sodium-metal halide rechargeable battery. Although the disclosed molten sodium-metal halide battery corresponds to a conventional sodium-metal chloride zebra battery system, the disclosed battery has a relatively low melting point which allows the battery to operate at a significantly lower temperature compared to conventional zebra battery systems Utilizing a molten eutectic mixture of sodium haloaluminate salts having a &lt; RTI ID = 0.0 &gt;

In one non-limiting embodiment of the disclosed invention, the rechargeable sodium battery comprises a negative electrode comprising metal sodium in a molten state. The anode comprises a mixture of NaX and MX, wherein X is a halogen selected from Cl, Br and I, and M is a metal selected from Ni, Fe and Zn. The anode 0 <δ <4, X '"4 , and X is Cl, Br, and selected other halogens of the formula NaAlX in I' _{- δ} X" mixed molten salt containing two or more salts, which may be represented as _δ anode Are disposed in the electrolyte. A sodium ion conductive solid electrolyte separates the cathode and the anode.

Mixed molten salt The anodic electrolytes contain two or more salts having the general formula NaAlX ' ₄ and NaAlX " ₄ at various molar ratios, wherein X' and X" are other halogens selected from Cl, Br and I. 9 is within a range, corresponding to the value of δ of 0.4 to 3.6: In a non-limiting embodiment, NaAlX _'4 dae NaAlX "molar ratio of ₄ to 9: 1 to 1.

The anode comprises a mixture of additional NaX or NaX compounds added to the mixed molten salt anodic electrolytes in a molar ratio of NaX: NaAlX ' _4-delta X " _delta ranging from 1: 1 to 3: At the cell operating temperature, the anode and the mixed molten salt anodic electrolyte is a molten liquid or a mixture of two phases wherein the mixed molten salt anodic electrolyte is usually liquid and the mixture of additional NaX or NaX compounds is a solid phase to be.

In one non-limiting embodiment, the molten salt bipolar electrolyte is NaAlBr _{2 . 8} I _{1 .2} .

In one non-limiting embodiment, NaX comprises NaBr.

In one non-limiting embodiment, MX comprises NiBr.

In one non-limiting embodiment, the molten salt a bipolar electrolyte comprises NaAlBr _{2 . 8} I _{1 .2} , NaX contains NaBr, and MX contains NiBr.

In one non-limiting embodiment, the sodium ion conductive solid electrolyte comprises a NaSICON electrolyte material. NaSICON electrolyte materials have a high sodium conductivity at battery operating temperatures.

In one non-limiting embodiment, the battery operates at a temperature in the range of 160 캜 to 220 캜.

In one non-limiting embodiment of the disclosed invention, the rechargeable sodium battery comprises a negative electrode comprising metal sodium in a molten state. The anode comprises a mixture of NaX and MX, wherein X is a halogen selected from Cl, Br and I and M is a metal selected from Ni, Fe and Zn. The anode 0 <δ <4, 0 < ω <4 and 0 <δ + ω <4 a, X ', X "and X'" are Cl, Br and I formula NaAlX 'of three different halogen selected from _{4 -隆 - ω} X " _δ X '" _ω . The mixed molten salt is disposed in the anodic electrolytes. A sodium ion conductive solid electrolyte separates the cathode and the anode.

Mixed molten salt The anodic electrolytes contain NaAlCl ₄ , NaAlBr ₄ and NaAlI ₄ at various molar ratios.

The anode comprises a mixture of additional NaX or NaX compounds added to the mixed molten salt anodic electrolytes in a molar ratio of NaX: NaAlX'4 _-delta-omega X " _delta X '" _o ranging from 1: 1 to 3: Excess NaX makes the bipolar electrolyte very basic. At the cell operating temperature, the anode and the mixed molten salt anodic electrolyte is a molten liquid or a mixture of two phases, wherein the mixed molten salt anodic electrolyte is usually liquid and the mixture of additional NaX or NaX compounds is solid.

In one non-limiting embodiment, NaX comprises NaBr.

In one non-limiting embodiment, MX comprises NiBr.

In one non-limiting embodiment, the sodium ion conductive solid electrolyte comprises a NaSICON electrolyte material. NaSICON electrolyte materials have a high sodium conductivity at battery operating temperatures.

In one non-limiting embodiment, the battery operates at a temperature in the range of 160 캜 to 220 캜.

In order that the manner in which the above-recited and other features and advantages of the present invention may be obtained will be readily apparent, the invention briefly described above will be described more specifically with reference to specific embodiments thereof, which are illustrated in the accompanying drawings. The present invention will now be described and explained with additional specificity and detail through the use of the accompanying drawings, with the understanding that this drawing depicts only some exemplary embodiments of the invention and, therefore, should not be construed as limiting its scope;
Figure 1 shows a schematic diagram of an exemplary embodiment of a molten sodium secondary battery in the process of discharging the battery.
Figure 2 shows a schematic diagram of an exemplary embodiment of a molten sodium secondary battery in the process of recharging the battery.
Figure 3 when operating at 185 ℃ 7 containing an excess of _{NaBr: 3 NaAlBr 4: NaAlI 4} (35: 35: 15: 15 NaBr: AlBr 3: NaI:.. AlI 3 ~ NaAlBr 2 8 I 1 2) &Lt; / RTI &gt; shows the cycling behavior of a sodium / nickel bromide cell in a positive electrode electrolyte comprising a mixture of &lt; RTI ID = 0.0 &gt;
Figure 4 shows the charge / discharge curve details of the battery reported in Figure 3 at an arbitrarily selected cycle at 196.6 hr.
Figure 5 shows the cycling behavior of a secondary sodium / nickel bromide cell constructed in the same manner as reported with respect to Figure 3, except that it was operated at a higher state of charge and a higher depth of discharge.

Reference throughout this specification to " one embodiment, "" one embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, throughout this specification, the phrases "in one embodiment "," in one embodiment ", and similar expressions may all refer to the same embodiment but are not necessarily so. Additionally, although the following description refers to various embodiments and aspects of various elements and aspects of the invention described, all described embodiments and examples are to be considered in all respects only illustrative and not restrictive in any way. Should be considered for.

Furthermore, the described features, structures, or characteristics of the present invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of suitable sodium cathodes, cathode materials, liquid anodic electrolyte solutions, sodium ion conductive electrolyte membranes, etc., in order to provide a thorough understanding of embodiments of the present invention. However, those skilled in the art will recognize that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so on. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring aspects of the present invention.

As described above, the secondary battery can be discharged and recharged, and this specification describes a battery arrangement and method for both states. While various forms of the term "recharge" refer to a second charge, those skilled in the relevant art will understand that the discussion of recharge is valid and applicable for the first or initial charge, and vice versa. Thus, for purposes of this disclosure, the terms "refilled "," refilled ", and "refillable" will each be compatible with the terms "refilled "," refilled &

The disclosed invention relates to a sodium / metal halide fused salt electrolyte battery operating at a relatively low temperature (&lt; 220 [deg.] C) compared to conventional sodium / metal chloride zebra battery systems operating at high temperature . Published sodium / metal halide battery negative electrode composed of NaSICON solid electrolyte membrane to separate the anode from the liquid sodium anode, an insoluble transition metal halide, preferably a metal bromide (NiBr ₂ or FeBr ₂ or ZnBr ₂ or a mixture of such bromide ) Is used. Another major difference between an open battery and a conventional Zebra battery system is that unlike the sodium / metal chloride cell, which includes a secondary electrolyte of sodium tetrachloroaluminate (NaAlCl ₄ ) in the anode portion, A molten eutectic mixture of an aluminate salt is used.

The sodium haloaluminate salt is selected from sodium chloroaluminate (NaAlCl ₄ ), sodium tetrabromoaluminate (NaAlBr ₄ ) and sodium tetraiodoaluminate (NaAlI ₄ ). For the purpose of specifying the formula of the two compounds eutectic mixture disclosed herein, X a 'and X "are Cl, and two different halogen selected from Br and I, 0 <δ <4 of NaAlX" _4-δ X _"δ Can be expressed. For the purposes of this specification, the chemical formulas of the three compound eutectic mixtures disclosed herein are such that X ', X "and X''' are three different halogens selected from Cl, Br and I and 0 <δ <4, 0 < And NaAlX ' _{4 - ? -} X " _? X'" _{? Where} 0 <? +? <4.

The sodium haloaluminate salts disclosed herein can be represented by the ratio of sodium halide and aluminum trihalide as follows:

NaX + AlX ₃ ↔ NaAlX ₄

Wherein X is a halogen selected from Cl, Br and I.

NaX: AlX ₃ ratio of 1: 1 is, is considered to be "neutral" halo sodium aluminate. When AlX ₃ is present in excess, the mixture is regarded as the "acidic". If excess NaX is present, the mixture is considered "basic &quot;.

One advantage of using metal halides such as nickel bromide is that in the presently disclosed invention, the anode has the ability to cyclize over a long period of time due to the alleviation of the dendrite found in the metal (nickel) chloride system at < to be. The use of NaSICON membranes with better lower temperature (&lt; 200 [deg.] C) conductivity than the beta "-alumina discussed below also achieves substantial current / voltage behavior of the sodium-nickel bromide batteries of the disclosed invention.

The disclosed invention provides a molten sodium-metal halide secondary battery that operates at an operating temperature of from about 100 ° C to about 250 ° C. 1 illustrates that the molten sodium secondary battery 10 comprises a cathode compartment 15 comprising a sodium metal cathode 20 and a cathode compartment 15 comprising a cathode 25). &Lt; / RTI &gt; The anode comprises a metal selected from Ni, Zn and Fe disposed in a positive electrode electrolyte 35 comprising a current collector 30 and a molten eutectic mixture of sodium haloaluminate salts (NaAlCl ₄ , NaAlBr ₄ and NaAlI ₄ ) . The sodium ion conductive electrolyte membrane 40 separates the negative electrode from the positive electrode and the positive electrode electrolyte 35. The sodium ion conductive electrolyte membrane 40 separates the first terminal 45 from the second terminal 50. In order to provide a better understanding of the described battery 10, a brief description of how the battery functions is provided below. Following this discussion, each component of the battery shown in Figure 1 will be discussed in more detail.

In view of the way in which the molten sodium secondary battery 10 now functions, the battery can function in virtually any suitable manner. In one example, Figure 1 illustrates a battery 10 is discharged and electron (e ^-) that it flows from the cathode 20 (e. G., A first terminal 45 a via), sodium sodium is oxidized from the cathode (20) Ion (Na &lt; ^{+ &} gt ^; ). 1 shows that these sodium ions are respectively transported from the sodium cathode 20 to the anode electrolyte 35 through the sodium ion conductive membrane 40.

In contrast, FIG. 2 shows that as the secondary battery 10 is recharged and electrons e ^- flow from an external power source (not shown) such as a charger into the sodium cathode 20, the battery 10 is discharged (As shown in FIG. 1) that occurs when the reaction occurs is reversed. Specifically, FIG. 2 shows that as the battery 10 is recharged, sodium ions (Na ⁺ ) flow from the anode electrolyte 35 through the electrolyte membrane 40, respectively, and sodium ions are reduced to form the sodium metal (Na) And is transported to the cathode 20.

With regard to the various components of the battery 10 now, the battery may include a cathode compartment 15 and an anode compartment 25 as mentioned above. In this regard, the two compartments may be of any suitable shape that allows the battery 10 to function as desired and may have any other suitable feature. For example, the cathode and anode compartments may be tubular, rectangular, or any other suitable shape. Also, the two compartments may have any suitable spatial relationship with each other. For example, FIG. 2 shows that the cathode compartment 15 and the anode compartment 25 may be adjacent to each other, while in other embodiments (not shown), the contents of the two compartments may be disposed between the electrolyte membrane 40 and any One compartment (e.g., cathode compartment) is disposed at least partially within another compartment (e.g., the anode compartment) while being separated by another compartment wall.

In connection with the cathode 20, the battery 10 may include any suitable sodium cathode 20 that allows the battery 10 to function (e.g., discharge and recharge) as desired. Some examples of suitable sodium cathode materials include, but are not limited to, sodium alloys comprising a substantially pure sodium sample and any other suitable sodium-containing cathode material. However, in certain embodiments, the cathode comprises or consists of a substantially pure amount of sodium. In this embodiment, since the melting point of pure sodium is about 98 占 폚, the sodium anode will melt above its temperature.

With respect to the positive electrode collector device 30, the positive electrode compartment 25 may comprise any suitable positive electrode to allow the battery to be charged and discharged as desired. For example, the anode can be any of the anode electrolytes 35 comprising a molten eutectic mixture of sodium haloaluminate salts, in virtually any collector 30 (in combination with metals generally seen as "M & ). In some non-limiting embodiments, the metal ("M") is selected from Ni, Zn, and Fe. In some non-limiting embodiments, the positive electrode collector may comprise wire, felt, plate, tube, mesh, foam and / or other suitable power collector configurations.

In some non-limiting embodiments, the reaction can occur at the cathode and anode, and the overall reaction as the cell 10 is discharged can occur as shown below:

Cathode 2Na ↔ 2Na ⁺ + 2e ^-

The anode M (X) ₂ + 2e ^- ↔ M + 2X ^-

Total 2Na + M (X) _2? M + 2NaX

Wherein X is a halogen selected from Cl, Br and I. In addition, some examples of the overall reaction that can occur at the cathode and anode and the total reaction that can occur during charging (or recharging) of the battery 10 can occur as shown below:

Cathode 2Na ⁺ + 2e ^- 2Na

Anode M + 2X ^- ↔ M (X) ₂ + 2e ^-

All M + 2NaX ↔ 2Na + M (X) ₂

The reaction shows that M has a divalent oxidation state (M ²⁺ ), but the anode can comprise a metal having a monovalent, trivalent, tetravalent or other oxidation state.

A positive electrode electrolyte 35 comprising a molten eutectic mixture of a sodium haloaluminate salt has been found to have good sodium ion conductivity that allows the cell 10 to function as desired. The positive electrode electrolyte 35 was intended to have a higher sodium ion conductivity than the electrolyte membrane 40. The sodium conductivity of the molten eutectic mixture of the sodium haloaluminate salt ranges from about 200 mS / cm to 500 mS / cm. The NaSICON conductivity may range from about 80 to about 220 mS / cm at a cell operating temperature of 150 [deg.] C to 200 [deg.] C.

Now with regard to the sodium ion conductive electrolyte membrane 40, the membrane may comprise any suitable material that selectively transports sodium ions and allows the cell 10 to function with the molten sodium and anodic electrolytes. In some embodiments, the electrolyte membrane comprises a NaSICON-type (sodium Super Ion Conductive) material. In this embodiment, the NaSICON-type material may comprise any known or novel NaSICON-type material suitable for use with the described battery 10. Some non-limiting examples of NaSICON-type compositions include, but are not limited to, Na ₃ Zr ₂ Si ₂ PO ₁₂ , Na _{1 + x} Si _x Zr ₂ P _{3 -x} O ₁₂ where x is selected from 1.6 to 2.4, , Y- doped _{NaSICON (Na 1 + x + y} Zr 2-y Y y Si x P 3-x O 12, Na 1 + x Zr 2 - y Y y Si x P 3 - x O 12 -y ( where , include x = 2, y = 0.12 Im)) and Fe- doped _{NaSICON (Na 3 Zr 2/3} Fe 4/3 P 3 O 12). Indeed, in certain embodiments, the NaSICON-type film comprises Na ₃ Si ₂ Zr ₂ PO ₁₂ . In another embodiment, the NaSICON-type film comprises a known or novel composite, cermet-supported NaSICON film. In such embodiments, the composite NaSICON film may comprise any suitable component including, but not limited to, a porous NaSICON-cermet layer comprising NiO / NaSICON or any other suitable cermet layer and a dense NaSICON layer. In yet another embodiment, the NaSICON film comprises monoclinic ceramics.

When the electrolyte membrane 40 of the battery contains a NaSICON-type material, the NaSICON-type material can provide various beneficial characteristics to the battery 10. [ In one example, this membrane selectively transports sodium ions, but does not allow the cathode 20 and the anode electrolyte 35 to mix, so that the membrane can help the cell to have a relatively stable shelf life at room temperature with minimal capacity loss have.

With reference now to terminals 45 and 50, the battery 10 may include any suitable terminal that is capable of electrically connecting the battery to an external circuit including, but not limited to, one or more batteries. In this regard, the terminal may comprise any suitable material and may be any suitable shape of any suitable size.

In addition to the aforementioned components, the battery 10 may optionally include any other suitable components. By way of a non-limiting example, FIG. 2 illustrates one embodiment that includes a battery 10 thermal management system 55, 60. An independent thermal management system can be associated with cathode and anode compartments. Alternatively, one thermal management system may be located within only one compartment or across the exterior of the battery 10. In such embodiments, the battery may comprise any suitable type of thermal management system capable of maintaining the battery within a suitable operating temperature range. Some examples of such thermal management systems include, but are not limited to, heaters, coolers, one or more temperature sensors, and suitable temperature control electrical networks.

The described battery 10 may function at any suitable operating temperature. In other words, as the cell is discharged and / or refilled, the sodium cathode and the anode electrolyte may have any suitable temperature. The cathode and anode compartments can operate at the same or different temperatures. Indeed, in some embodiments, the cell functions at an operating temperature as high as a temperature selected from about 260 캜, about 240 캜 and about 220 캜. In addition, in this embodiment, as the cell functions, the temperature of the cathode and / or anode compartment may be as low as selected from about 160 캜, about 170 캜, about 180 캜 and about 200 캜. Indeed, in some embodiments, as the cell functions, the temperature of the cathode and / or anode compartment may be between about 160 캜 and about 260 캜. In another embodiment, the cell functions at a temperature of about 180 ° C to about 220 ° C. However, in another embodiment, as the cell functions, the temperature of the cathode and / or anode compartment is about 200 ° C ± about 10 ° C.

In certain embodiments, the temperature range is dependent on the melting point of the electrolyte used. For example, in one embodiment, the cell may be operated at a temperature of at least 10-20 DEG C above the melting point of the electrolyte. As the electrolyte increases its conductivity as the temperature increases, there is inevitably no upper limit for the electrolyte. In one embodiment, for example, sodium is dissolved in about 98 ℃ NaAlCl ₃ I electrolyte has a melting point of about 85 ℃. It is therefore possible to operate the battery at temperatures as low as 100 ° C.

The following examples are intended to illustrate various embodiments within the scope of the present invention and aspects thereof. It is understood that these are given by way of example only, and the following examples do not cover or encompass many types of embodiments of the invention which may be made in accordance with the present invention.

Example  One

The preparation of the molten sodium-metal bromide secondary cell used in the examples disclosed herein may be as follows: NaSICON (Na Super Ionic Conductor) The solid electrolyte membrane is placed in a glass tube (or alumina tube) It is filled with a sealed and molten sodium metal (cathode). A stainless steel or Ni or Mo metal current collector rod is submerged in sodium metal to provide electrical contact with the cathode. The glass tube is placed inside another glass bottle with a lid that tightly seals the glass tube to hang it and keep it in the space inside the glass bottle.

Insoluble anodes are located in the bottle opposite the NaSICON membrane. The insoluble anodes are prepared by thoroughly mixing Ni metal particles with NaBr powder and pressing them with pellets. The porosity of the anode is in the range of 15 to 70%, preferably in the range of 35 to 55%. Nickel or rods, mesh or other suitable forms of carbon current collector are used to provide electrical contact with the anode. Based on the initial amount of NaBr, the theoretical capacity of the anode used in this example is about 200 mAh. In one embodiment, the initial amount of Ni can be 1.31 g and the initial amount of NaBr can be 0.77 g.

The anode portion containing the molten salt electrolyte is separated from the cathode portion by a NaSICON solid electrolyte membrane of 0.72 cm in diameter (an active region through which Na ions are conducted) and has a thickness of 0.1 cm.

Example  2

Several other mixtures of NaAlBr ₄ + NaAlI ₄ (or NaAlCl ₄ ) molten salt electrolytes are placed in the bottle described in Example 1 so that the anode is immersed in the electrolyte. This electrolyte serves to conduct sodium ions from the solid electrolyte to the reaction site of the metal bromide in the anode. Mixed NaAlBr ₄ + NaAlI ₄ (or NaAlCl ₄ ) The molten salt electrolyte is eutectic and melts in the temperature range of 150 ° C to 180 ° C depending on the composition of the mixture. These melting points are lower than the respective salts as shown in Table 1 below. Table 1 also shows the melting points of three different mixtures at various ratios of NaAlBr ₄ and NaAlI ₄ with a single compound. NaAlBr ₄ a number of compositions (compositions 2 or 3) is preferred to operate the present battery. To specifically sodium of greater than shown in Table 3, column halide (NaBr: 3 of NaI: 1 ratio) and _{NaBr: AlBr 3: NaI: AlI} 3 35: 35: 15: made by mixing 15 NaAlBr _{2. 8} I 3 corresponding to the composition of the _first composition _0.2 was used in the disclosed battery operation. Specifically, 0.91 moles NaBr, and NaI 0.39 molar excess is a NaAlBr used herein in Example _{2. 8} I _{1 .2} .

There are five purposes for the addition of excess sodium bromide and sodium iodide:

[1] The solubility of nickel halide must be minimized in the molten salt electrolyte to achieve high charge and discharge rates of nickel-nickel halide cathodes. Supersaturation of the electrolyte makes it possible further reduce the solubility of nickel halide and may have a rapid solid-phase reversible electrode reaction rate of the transition to NiX ₂ from Ni during the charge / discharge process (the present embodiment example, NiBr _2).

[2] Neutral sodium halo aluminate solution utilized (where the single or mixed, whether the halogen is present NaX:: ratio of AlX ₃ is _1: 1, for example NaAlBr _{2 8} I _{1 2)} is the electrolyte during the charging process, As this sodium is lost, there is a risk that the solubility of the nickel halide in the acidic environment (ie, lack of NaX) increases significantly. Although the solution may initially be neutral, there may be some zones that become acidic in the electrolyte. Which results in the loss of the capacity of the cathode due to depletion of the sodium halide (NaBr in this example) from the cathode after its formation. The nickel halide solubility is also higher in the acidic sodium halohaluminate solution. The addition of sodium halide in excess in the electrolyte prevents the NaBr and NiBr ₂ is exhausted from the cathode.

[3] There is a possibility that the capacity of the cathode can be increased by overcharging it. The excess Na halide in the electrolyte causes the formation of a new nickel halide at the electrode after overcharging. This helps maintain the cathode's battery capacity retention during long-term cycling.

[4] While the disclosed invention utilizes a "very basic" electrolyte, the Zebra battery utilizes a neat / slightly basic sodium chloride sodium aluminate catholyte. There can be significant differences between the liquid compositions in the basic electrolyte having a salt of more than neutral electrolyte. It is possible that the difference between the two types of electrolytes in the liquid composition leads to a better performance of the battery. As a non-limiting example, a slightly basic electrolyte may comprise about 50.1% to 53% sodium halide. A very basic electrolyte may have a sodium halide greater than about 55% (e.g., 55:45 NaX: AlX3). In one embodiment, the excess sodium halide salt is in a ratio of 70:30 (NaX: AlX3).

[5] U.S. application no. As disclosed in 2014 / 0170443A1, having an excess of sodium halide in the electrolyte will provide a higher anti-corrosion temperature of the NaSICON film which increases the lifetime of the battery operation. The high temperature stability of NaSICON in NaX solution follows the order of NaI> NaBr> NaCl.

Example  3

The electrode reaction in a molten sodium-metal bromide secondary cell of a nickel metal anode during charge / discharge as described in Example 1 is as follows:

NiBr ₂ + 2Na? Ni + 2NaBr At about 180 ° C, E ₀ = 2.48 V

The cell is manufactured in a discharge state in which the initial composition of the anode is Ni metal and sodium bromide. Cells 7 containing NaBr of excess: 3 NaAlBr _4: NaAlI ₄ positive electrolyte comprising a mixture of (35: 35: 15: 15 NaBr: AlBr 3:: NaI.. AlI 3 ~ NaAlBr 2 8 I 1 2) . Figure 3 shows the cycling behavior of the cell when operated at 185 ° C. The cell is first charged to a 60% state of charge (SOC) at a C / 10 rate (based on the 200 mAh capacity of the anode) and then 60-40% SOC (20% The cycling starts in the charging state range of FIG. The charge-discharge C-rate continues to increase until the cell cycles at the C / 3 rate, corresponding to a current density of 100 mA per square cm of NaSICON film area.

Figure 3 shows that the cell was operated for 100 cycles at this C / 3 rate. After 100 cycles, the cell was further cycled at a current density of 91 cycles at a wider charge state (SOC) range of 60 to 20%. The detailed charge / discharge curve of the cycle arbitrarily selected from 196.6 hours is shown in FIG. Analysis of this cycle data shows a columbic efficiency of about 100% and an energy efficiency of 83.1%. The area specific resistance (ASR) normalized to the membrane area for charge and discharge is 2.3 V and 2.17 V, respectively.

The second cell was manufactured in the manner described above and was operated at a higher charge state (SOC) range (90-10%), i.e. at a higher discharge depth (about 80%) and the operating result data is shown in Figure 5 . The current efficiency of this cell was> 98%, which represents a substantial coulombic efficiency beyond the 93+ cycles in which the cell operated. The energy efficiency of all of the example cells exceeded 80%.

While specific embodiments and examples of the invention have been shown and described, numerous modifications will come to mind without departing from the scope of the invention in any way, and the scope of protection is limited only by the scope of the claims which follow.

Claims (20)

A negative electrode comprising metal sodium in a molten state;
Formula _{NaAlX '4 - δ X "δ} ( and where, 0 <δ <4, X ' and X" is a different halogen being selected from Cl, Br and I) mixed melt containing two or more salts, which may be represented as A cathode comprising a mixture of NaX and MX, wherein X is a halogen selected from Cl, Br and I, and M is a metal selected from Ni, Fe and Zn; And
A sodium ion rechargeable sodium battery comprising a sodium ion conductive solid electrolyte provided between a cathode and an anode. The rechargeable sodium battery according to claim 1, wherein the mixed molten salt cathode electrolyte comprises two or more salts having various molar ratios of the general formula NaAlX ' ₄ and NaAlX " ₄ . The method of claim 2, wherein the NaAlX ' ₄ Wherein the molar ratio of NaAlX " to NaAlX " ₄ is in the range of 9: 1 to 1: 9 and the corresponding delta value is between 0.4 and 3.6. The method of claim 1, wherein the anode comprises a mixture of additional NaX or NaX compounds added to the mixed molten salt anodic electrolytes in a molar ratio of NaX: NaAlX ' _{4 - delta} X " _delta ranging from 1: 1 to 3: 1 Rechargeable sodium battery. 5. The rechargeable battery of claim 4 wherein the anodic and mixed molten salt anodic electrolytes are molten liquid or a mixture of two phases wherein the mixed molten salt anodic electrolyte is usually a liquid phase and the additional NaX or NaX compound mixture is a solid phase. The method of claim 1, wherein the molten salt is a NaAlBr _{2 . 8} I _{1 .2} . The rechargeable sodium battery of claim 1, wherein the NaX comprises NaBr. The rechargeable sodium battery of claim 1, wherein MX comprises NiBr. The method of claim 1, wherein the molten salt is a NaAlBr _{2 . 8} I _{1 .2} , NaX comprises NaBr, and MX comprises NiBr. The method of claim 9, wherein the positive electrode is mixed in the first molten salt electrolyte anode: NaBr range of 1: 1 to 3 NaAlBr _{2. 8} I _{1 . 2 &lt; / RTI} &gt; molar ratio. 11. The rechargeable sodium battery of claim 10, wherein the sodium ion conductive solid electrolyte comprises NaSICON electrolyte material. The rechargeable sodium battery of claim 1, wherein the sodium ion conductive solid electrolyte comprises a NaSICON electrolyte material. 2. The rechargeable sodium battery of claim 1, wherein the battery operates at a temperature in the range of 160 &lt; 0 &gt; C to 220 &lt; 0 &gt; C. A negative electrode comprising metal sodium in a molten state;
Formula _{NaAlX '4 -δ- ω X "δ} X'" ω ( where, 0 <δ <4, 0 <ω <4 and 0 <δ + ω <4 a, X ', X "and X'" is Cl , Br, and I), NaX and MX, wherein X is selected from the group consisting of halogen selected from Cl, Br and I And M is a metal selected from Ni, Fe and Zn); And
A sodium ion rechargeable sodium battery comprising a sodium ion conductive solid electrolyte provided between a cathode and an anode. The method of claim 14 wherein the mixed molten salt electrolyte is the cathode in the rechargeable battery comprises a sodium NaAlCl _4, NaAlBr NaAlI ₄ and ₄ of different molar ratio. The method of claim 14, wherein the positive electrode is mixed in the first molten salt electrolyte anode: NaX range of 1: 1 to _{3 NaAlX '4 -δ- ω X "} δ X'" of the additional compound is added NaX or NaX mole ratio _ω Lt; RTI ID = 0.0 &gt; rechargeable &lt; / RTI &gt; sodium battery. 17. The rechargeable battery of claim 16, wherein the anodic and mixed molten salt anodic electrolytes are molten liquid or a mixture of two phases, wherein the mixed molten salt anodic electrolyte is usually a liquid phase and the additional NaX or NaX compound mixture is a solid phase. 17. The rechargeable sodium battery of claim 16, wherein the sodium ion conductive solid electrolyte comprises NaSICON electrolyte material. 17. The rechargeable sodium battery of claim 16 operating at a temperature in the range of 160 &lt; 0 &gt; C to 220 &lt; 0 &gt; C. 17. The rechargeable sodium battery of claim 16, wherein NaX comprises NaBr and MX comprises NiBr.

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